This invention relates to a process for the ultimate production of unsaturated alcohols having the formula ##STR3## in which R, R' and R" are independently hydrogen or alkyl groups having from 1 to 20 carbon atoms each. Such compounds will be referred to hereinafter as 2-alken-1-ols. This invention also relates to novel intermediates for production of such compounds and to novel processes for producing such compounds and intermediates.
A number of compounds of this type, in both cis and trans isomers, are already known and have been found useful as chemical intermediates and as flavoring and other sensory agents. For example, the compound trans-2-hexen-1-ol is useful in flavoring strawberry and orange juices.
As will be discussed hereinafter, this application finds greatest use in the production of cis-2-alken-1-ols. Such compounds have been prepared by various methods as described, for example, in the article by Delady, Bull. Soc. Chem., Vol. 5, No. 3 (1936) pp. 2375-2382, and particularly on page 2380 (preparation of 2-decen-1-ol by reaction of .beta.-heptylylallyl acetate with caustic soda) and Crombie, et al., J. Chem. Soc., 1955, pp. 4244-4249 (hydrogenation of hex-2-yn-1-ol). Another process, rather complicated in nature, is described in a letter by Zweifel, et al., J. Am. Chem. Soc., Vol. 89, pp. 5085-5086 (1967). In this process, an acetylenic compound is reacted with a dialkylaluminum hydride and an alkyllithium compound to produce an intermediate trans-vinylalanate compound which can then be reacted with paraformaldehyde to produce cis-.alpha.,.beta.-unsaturated alcohols.
In an article by Malpass, et al., J. Org. Chem., Vol. 42, pp. 2712-2715 (1977) and in U.S. Pat. No. 4,069,260, there is described a process for production of cis-3-alken-1-ols by reaction of an unsaturated aluminum alkyl with various alkylene epoxides. Such a process provides for the production of such alkenols directly from the corresponding cis-substituted aluminum compounds, rather than by the complicated methods heretofore used. The letter by Zweifel, et al. states that in their process, an isomeric shift occurs in that reaction of the trans-vinylalanates formed using the alkyl lithium compounds, with paraformaldehyde, results in cis-unsaturated alcohols.
It would also be desirable to provide a process by which trans-unsaturated alcohols can be produced from the corresponding trans-unsaturated aluminum compounds.